The Rockies have always had a huge home-field advantage (HFA) at Coors. From 1993 to 2001, Colorado has played .545 at home, but only .395 on the road. That's the equivalent of the difference between going 89-73 and 64-98.  Why such a big difference? I have some ideas I'm working on, but the most obvious one -- although it's not that big, as we will see -- is that higher scoring naturally, mathematically, leads to a bigger HFA. When teams play better at home than on the road -- for whatever reason --the manifestation of "better" is in physical performance, not winning percentage as such ..read more

(Part I is here.) 20 percent of drivers own diesel cars, and the other 80 percent own regular (gasoline) cars. Diesels are, on average, less reliable than regular cars. The average diesel costs $2,000 a year in service, while the average regular car only costs $1,000.  Researchers wonder if there's a way to reduce costs. Maybe diesels cost more partly because mechanics don't like them, or are unfamiliar with them? They create a regression that controls for the model, age, and mileage of the car, as well as driver age and habits. But they also include a variable for whether the mechanic ..read more

Are MLB umpires racially biased? There's a recent new study that claims they are. The author, who wrote it as an undergrad thesis, mentioned it on Twitter, and when I checked a week or so later, there were lots of articles and links to it. (Here, for instance, is a Baseball Prospectus post reporting on it.  And here's a Yahoo! report.) The study tried to figure whether umpires make more bad calls against batters* of a race other than theirs (where there is no "umpire-batter match," or "UBM," as the literature calls it). It ran regressions on called pitches from 2008 to 2020, to figure ou ..read more

In a previous post, I noticed that the DRS estimates of team fielding seemed much too high in many cases. In fact, the spread (standard deviation) of team DRS was almost three times as high as other methods (UZR and OAA). For instance, here are the three competing systems for the 2016 Chicago Cubs: UZR: +43 runs (range) OAA: +29 runs DRS: +96 runs (107 - 11 for catcher framing) Since I wrote that, the DRS people (Baseball Info Solutions, or BIS) have issued significant corrections for the 2018 and 2019 seasons (and smaller corrections for 2017). It seems the MLB feeds were off in their timi ..read more

(This is part 3.  Part 1 is here; part 2 is here.) ------ Last post, we estimated that in 2018, Phillies fielders were 3 outs better than league average when Aaron Nola was on the mound. That estimate was based on the team's BAbip and Nola's own BAbip. Our first step was to estimate the Phillies' overall fielding performance from their BAbip. We had to do that because BAbip is a combination of both pitching and fielding, and we had to guess how to split those up. To do that, we just used the overall ratio of fielding BAbip to overall BAbip, which was 47 percent. So we figured that the ..read more

(Part 1 is here.  This is Part 2.  If you want to skip the math and just want the formula, it's at the bottom of this post.) ------ When evaluating a pitcher, you want to account for how good his fielders were. The "traditional" way of doing that is, you scale the team fielding to the pitcher. Suppose a pitcher was +20 plays better than normal, and his team fielding was -5 for the season. If the pitcher pitched 10 percent of the team innings, you might figure the fielding cost him 0.5 runs, and adjust him from +20 to +20.5. I have argued that this isn't right. Fielding performance ..read more

(Update, 2020-12-29: This is take 2. I had posted this a few days ago, but, after further research, I tweaked the numbers and this is the result. Explanations are in the text.) ----- Suppose a team has a good year in terms of opposition batted ball quality. Instead of giving up a batting average on balls in play (BAbip) of .300, their opponents hit only .280. In other words, they were .020 better than average in turning (inside-the-park) batted balls into outs.  How much of those "20 points" was because of the fielders, and how much was because of the pitcher? Thanks to previous work by T ..read more

Suppose a team has a good year in terms of opposition batted ball quality. Instead of giving up a batting average on balls in play (BAbip) of .300, their opponents hit only .280. In other words, they were .020 better than average in turning (inside-the-park) batted balls into outs.  How much of those "20 points" was because of the fielders, and how much was because of the pitcher? Thanks to previous work by Tom Tango, Sky Andrecheck, and others, I think we have what we need to figure this out. If you don't want to see the math or logic, just head to the last section of this post for the t ..read more

I missed a post Tango wrote back in 2019 about park factors. In the comments, he said, "That’s one place where we failed with our park factors, using actual runs instead of "component" runs. They should be based on Linear Weights or RC or wOBA, something like that. "Using actual runs means introducing unnecessary random variation in the mix." Yup. One of those bits of brilliance that's obvious in retrospect. The idea is, there's a certain amount of luck involved in turning batting events into runs, which depends on the sequence -- in other words, "clutch hitting," which is thought to be ..read more

This guest post is from occasional contributor Charlie Pavitt. Here's a link to some of Charlie's previous posts. ----- Induction into the National Baseball Hall of Fame (HOF) is of course the highest honor available to those associated with the game.  When one thinks of the HOF, one first thinks of the greatest players, such as the first five inductees in 1936 (Cobb, Johnson, Matthewson, Ruth, and Wagner). But other categories of contributors were added almost immediately; league presidents (Morgan Bulkeley, Ban Johnson) and managers (Mack, McGraw) plus George Wright in 1937, p ..read more